Field of the Invention
The present invention relates to use of certain chain transfer agents to control molecular weight of addition mass polymerization of certain polycycloolefinic monomers. More specifically, the present invention relates to use of a series of substituted bicycloalkenes as chain transfer agents in the addition mass polymerization of a series of functionalized norbornene-type monomers. This invention also relates to compositions containing bicycloalkenes as chain transfer agents in forming “in mold” polycycloolefinic polymers by addition mass polymerization.
Description of the Art
Cyclic olefin polymers, such as polynorbornenes (PNBs), are widely used in a variety of electronic, optoelectronic and other applications, and therefore, methods of making such PNBs in an industrial scale are of importance. It is well known in the literature that various functionalized PNBs can be synthesized by employing suitable starting norbornene monomers by addition polymerization using a variety of transition metal catalysts and procatalysts. See for example, U.S. Pat. No. 7,989,570, pertinent portions of which are incorporated herein by reference.
It is also known in the literature that certain of the aforementioned vinyl addition polymerization methods result in very high molecular weight polymers, which may not always be desirable, such as for example, high molecular weight polymers become less soluble in commonly used solvents, and therefore, can't be used in many applications involving any solvent based compositions. Accordingly, it has been reported in the literature that certain chain transfer agents can be used in the vinyl addition polymerization methods in order to control the molecular weight. See for example, U.S. Pat. No. 5,468,819, where it is disclosed use of an olefinic chain transfer agent to control the molecular weight of an addition polymer in solution. Similarly, U.S. Pat. No. 7,759,439 and U.S. Pat. No. 7,863,394 disclose respectively use of formic acid and non-olefinic compound (such as silane, germane and stannane) as chain transfer agent in solution phase addition polymerization.
In some applications, such as, electronics applications, the polymer formed from the addition solution polymerization must undergo several process steps which involve removing the metal catalyst and the solvent. This further may involve different polymerization solvent and carrier solvent for the compositions employed in the electronic applications. These additional steps also create considerable amounts of solid and liquid waste which needs to be disposed, which are environmentally not friendly and also expensive.
Accordingly, there is a need to develop a method to mass addition polymerization of polycycloolefinic monomers such that controlled molecular weight polymers can be prepared without adversely affecting the reactivity and final monomer conversion. More importantly, such polymers are formed without the use of any solvents, and should feature good thermal and mechanical properties.
Accordingly, it is an object of this invention to provide a series of bicycloalkenes having utility as chain transfer agents in mass addition polymerization of a variety of cycloolefinic monomers.
It is also an object of this invention to provide compositions to form controlled molecular weight polymers by mass addition polymerization techniques as disclosed herein.
Other objects and further scope of the applicability of the present invention will become apparent from the detailed description that follows.